In the recent development of semiconductor fabrication technology, the continuous miniaturization in IC devices demands more stringent requirements in the fabrication environment and contamination control. It has been recognized that an inert mini-environment may be the only solution to future fabrication technologies when the device size is further reduced. In order to eliminate micro-contamination and to reduce native oxide growth on silicon surfaces, the wafer processing and the loading/unloading procedures of a process tool must be enclosed in an extremely high cleanliness mini-environment that is constantly flushed with ultrapure nitrogen that contains no oxygen or moisture. In order to maintain the high cleanliness class inside the process tool the loading and unloading sections of the process tool must be handled automatically by an input/output device such as a SMIF (standard mechanical interfaces) apparatus. A cassette of wafer can be transported into the process tool by a SMIF pod situated-on top of the SMIF apparatus.
Usually, wafer cassettes having sealing cover can be divided into two types, the mechanical-opened and the manual-opened. Wafer cassettes having mechanical-opened cover are always used in SMIF apparatus, and wafer cassettes having manual-opened cover are always used by means of maneuvering.
Please refer to FIGS. 1 and 2. They illustrate a wafer carrying system having manual-opened cover according to the prior art. The wafer carrying system includes a wafer cassette 10 and a cover 11. Meanwhile the wafer cassette 10 and the cover 11 have to be integrated via an opener, as shown in FIG. 2. The opener 20 includes two protrudent devices for engaging into two controlling troughs 12 of the cover 11, so as to rotate the two controlling troughs 12 to drive four tenons 13 thereof, thereby four tenons 13 being engaged into four troughs 14 and the combination of the wafer cassette 10 and the cover 11 finishing. Plural wafers 15 carried by said wafer cassette 10 are placed in an isolating region from the dust and the static electricity.
When separating the combination of the wafer cassette 10 and the cover 11, and opening the cover 11, an operator must use the opener 20. The operator pull a handle 21 of the opener 20 for rotating the two controlling troughs 12 to drive the four tenons 13. Then the cover 11 can be opened, but the operator has to take away the cover 11 with the opener 20 and find some space to place the cover 11 with the opener 20. After wafer 15 is taken out from the wafer cassette 10, the operator takes the cover 11 with the opener 20 to execute the above steps for combining the wafer cassette 10 and the cover 11 to close. It is not convenient to execute such complicated steps and provide extra space for placing the cover 11 with the opener 20. The wafer carrying system is therefore of limited use.
Therefore, it is tried to rectify those drawbacks and provide a wafer cassette with a manual-opened cover by the present applicant.